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Management practices of fertilization

for improving crop production and

creating safe environment

Jen-Hshuan Chen

Professor and Chair of the

Department of Soil and

Environmental Sciences, NCHU

Thanks

Food & Fertilizers Technology Center (FFTC)

Taichung District Agricultural Research and Extension Station, Council of Agriculture

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Jen-Hshuan Chen

Education: PhD, Department of Agronomy, Purdue University, USA (1989)

Position: Professor and Chair,

Department of Soil and Environmental Sciences,

National Chung-Hsing University. Taiwan, ROC

Major field: Fertilizer and Soil Fertility, Soil Management, Agricultural Waste Treatment

Introduction

Fertilizers have sustained world

agriculture and global population .

However, lacking, imbalanced,

inappropriate or excessive use of

nutrients in agricultural systems remains

a concern.

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Traditional fertilization usually focused on

improving the growth and/or the quality

of crops and ignored the possible risk of

negative impact on soil and environment.

Introduction

Essential Nutrients

The plant cannot complete its life cycle

without these nutrients.

The nutrient’s function cannot be replaced

by another nutrient.

The nutrient is directly involved in the plant’s

growth and reproduction.

Most plants need these nutrients to survive.

Nutrients must be available not only in sufficient

amounts but also in appropriate ratios.

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Element Chemical symbol Form(s) taken up by plant

Carbon C CO2

Hydrogen H H2O

Oxygen O H2O , O2

Nitrogen N NH4+ , NO3

-

Phosphorus P H2PO4- , HPO4

2-

Potassium K K+

Calcium Ca Ca2+

Magnesium Mg Mg2+

Sulfur S SO42-

Nutrients essential to plant growth- Macronutrients

Element Chemical symbol Form(s) taken up by plant

Iron Fe Fe2+ , Fe3+

Zinc Zn Zn2+ , Zn(OH)2

Manganese Mn Mn2+

Copper Cu Cu2+

Boron B B(OH)3

Molybdenum Mo MoO42-

Chlorine Cl Cl-

Nutrients essential to plant growth- Micronutrients

0

0

0

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Essential nutrients for plants and animals

Major Elements Micronutrients

Plants and Animals

Calcium (Ca), Carbon (C)

Hydrogen (H), Magnesium (Mg)

Nitrogen (N), Oxygen (O)

Phosphorus (P), Sulfur (S)

Chlorine (Cl), Copper (Cu), Iron (Fe), Manganese (Mn), Molybdenum (Mo)

Plants only

Boron (B)

Animals only

Healthy plant

Healthy life

Arsenic (As), Chromium (Cr), Fluorine (F), Iodine (I), Nickel (Ni), Selenium (Se), Vanadium (V)

Effect of increasing the supply of a nutrient on

crop yield

Amount of nutrient

Yie

ld

1. Ideal conditions

2. Best field conditions

3. Poor field conditions

A A C A

B D

x

y

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Liebig's

law of minimum (Barrel theory)

Increasing the amount of

plentiful nutrients did not increase plant

growth. Only by increasing the amount of the

limiting nutrient (the one most scarce in

relation to "need") was the growth of a plant

or crop improved.

The use of fertilizer improves crop

performance, but at some point, adding

increasingly more fertilizer improves

the yield by less per unit of fertilizer,

and excessive quantities can even

reduce the yield.

Law of diminishing returns

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Fertilizer efficiency

N fertilizer：Flood field：30 ~ 40 %

Dry field：50 ~ 70%

P fertilizer：5 ~ 20 %

K fertilizer：40 ~ 60 %

Pathways of loss：

N: denitrification, ammonium volatilization, leaching, soil erosion, fixation

P: fixation, soil erosion leaching,

K：leaching, soil erosion, fixation

Problems caused by fertilizer abuse

1. Harmful effects on human health

2. Harmful effects on environment

3. Reduced soil quality

(1) Acidification

(2) Accumulation of toxic elements

(3) Accumulation of salt

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Problems caused by fertilizer abuse

4. Contribution to climate change and air

pollution

5. Harmful on plant growth

(1) Diminished plant health

(2) Attract pests and diseases

Harmful effects on human health

Nitrates (NO3-)can contaminate drinking water, which

causes a baby's face to turn blue from a lack of oxygen

in the blood. This is known as methemoglobinemia

(Methemoglobin is a form of hemoglobin that contains

ferric [Fe3+] iron and has a decreased ability to bind

oxygen.)

Farmers and workers exposed to fertilizers over long

periods of time exhibit symptoms of neurological

damage, including dizziness, and headaches.

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Harmful effects on the

environment

When excessive amounts of phosphorus enter

lakes and streams, it stimulates the growth of

algae and other aquatic microorganisms.

eutrophication

Eutrophication

Results “Off flavor” drinking water Reduces water quality Lowers oxygen levels Causes reduction and shifts in aquatic populations

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Reduction of soil quality by fertilizer abuse

Decrease of soil organic matter

Detriment to soil structure

Salinization(salt accumulation)

Acidification

Heavy metal accumulation

Abuse of fertilizer

Poor management

Contribution to climate change

and air pollution

Over fertilization of nitrogen to paddy soils

or soils with poor drainage can contribute to

the release of greenhouse gases such as

carbon dioxide(CO2), methane(CH4) and

nitrous oxide(N2O).

Excess greenhouse gases trapped in the

atmosphere may be contributing to the

increase of land and ocean surface

temperatures.

Causes storms, floods, heat, air pollutants,

shortage of food supply

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Harmful on plant growth

(1) Diminished plant health

Over-application of fertilizer to plants may damage the

plant and reduce crop yield.

Over fertilization often causes root burn due to the

roots of plants which suffer damage from excess salt.

(2) Attract pests and diseases Plants that produce greener, more lush leaves because

of over fertilization may attract more pests. Overuse

of fertilizers stress plants, increasing their susceptibility

to various diseases and insect pests.

Best management Practices of

fertilization (Colorado Legislature,

1990)

1. Improve fertilizer efficiency。

2. Improve or maintain crop yield

and quality。

3. Less impact on soil and

environment。

The act calls for education and training of

all producers and farmers in the proper

use of pesticides and fertilizers.

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4R , BMP of fertilizer (IFA)

Apply the “Right Rate” of fertilizer to match

nutrient supply with crop requirements;

Apply fertilizer at the “Right Time” so nutrients will

be available when crop demand is high;

Apply fertilizer in the “Right Place” or location

where the crop can access the nutrients most

effectively;

Use the “Right Form” of fertilizers that are in or are

easily converted over to compounds best used by the

target crop.

Right Product(s)/ Source(s)

Right Rate

Right Time

Right Place

Balanced fertilization (N, P, K, secondary and micronutrients)

Nutrient form (urea, nitrate, ammonium)

Soil testing

Yield goal

analysis

Crop removal balance

Plant tissue analysis

Crop inspection

Record keeping

Application

timing

Slow- and controlled-release

Fertilizers

Urease and nitrification inhibitors

Application

method

Incorporation of fertilizer

Applicator maintenance and calibration

Examples of elements of FBMPs (IFA, 2009)

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The use of chemical fertilizers, organic

fertilizers or biofertilizers, has its advantages

and disadvantages on nutrient supply, crop

growth and environmental quality.

These advantages need to be integrated in

order to get the most out of each type of

fertilizer, and achieve the balanced nutrient

management for crop growth.

Chemical fertilization

Advantages

Impressive yield increase

Supply nutrients in water-soluble form to ensure rapid availability to crop.

Relative high in nutrient content, only relative small amounts are required for crop growth.

The price is lower than organic fertilizer, and more accepted by farmers.

Disadvantages

Availability of nutrients

decline fast.

Nutrients are easily lost from soil.

Over application will easily happen, thus causing some negative effects, such as reducing soil fertility, polluting water resource, destroying microbes and friendly insects…etc.

Reduces or inhibits soil biological activity

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Organic fertilization

Advantages

Nutrient supply is more

balanced.

Enhance soil biological activity and encourage the growth of beneficial microorganisms.

Increase OM content of soil, and improve soil physical, chemical and biological properties.

Enhance root growth due to better soil condition.

Disadvantages

Comparative low in

nutrient content.

Too low nutrients release rate to meet crop requirement in a short time.

Highly variable nutrient composition and cost is higher.

Long-term and/or heavy application may result in salts, nutrients and heavy metals accumulation.

Biofertilizers

Rhizobia

Azotobacter, Azospirillum

Phosphate-Solubilizing bacteria

Vescular arbuscular mycorrhizae, VAM

Potassium-Solubilizing bacteria

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Biofertilizer usuage

Advantages

Stimulate plant growth

Help plant to against adverse environmental stress

Improves water and nutrients absorption by plant from the soil.

Reduce the use of chemical fertilizer.

Reduce plant disease.

Disadvantages

Does not directly supply

any nutrient to crop.

Some need specific host, eg. rhizobia

Strict usage environment and storage condition

Short shelf life, lack of suitable carrier materials, susceptible to high temperature, salt accumulation, excess fertilizer addition , and waterlogging.

Quality stability problem.

Right Placement

Correct placement of fertilizers in the

plant rooting zone often improves the

efficiency of nutrient uptake by plants and

consequently encourages maximum

yields of crops.

Maximizing crop uptake also reduces the

potential for losses of nutrients.

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Methods of application: Broadcast

Broadcast is generally preferred for

plants that are actively growing over

most (or all) of the soil surface, such as

pastures, alfalfa, clovers.

Broadcast applications generally are less

efficient and leave more P at the soil

surface than banding.

Methods of application: Band

For row crops, banding is generally the most

efficient method for applying micronutrient

fertilizers.

Banded applications below seeding depth,

placement with the seed and/or broadcast-

incorporated applications are superior to

surface broadcast treatments because they

minimize losses of phosphorus.

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Methods of application: Fertigation

Fertigation is the application of

water-soluble fertilizers by injecting

fertilizer into irrigation water.

Advantages

Saves fertilizers

Saves water

Improves crop growth and quality

Fertilizers are applied directly to leaves. The

method is almost invariably used to apply

water-soluble straight fertilizers and used

especially for high value crops such as fruits.

Foliar applications of macronutrients are

generally not cost effective because plants’

requirements for macronutrients are greater

than the amount that can be taken up

through the plant leaves.

Methods of application: Foliar

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Under which conditions should we

use foliar feeding?

Limiting conditions - A foliar feeding is

recommended when environmental conditions limit the

uptake of nutrients by roots. This include temperature ,

water stress, root disease etc.

Nutrient deficiency symptoms - One of the

advantages of foliar feeding is the quick response of the

plant to the nutrient application.

In specific growth stages – Plants require

different amounts of nutrients in different growth stages.

Foliar applications of essential nutrients during key

stages can improve yield and quality.

Right time — match the nutrient

requirement of crop (Splitting application)

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Erosion control BMPs for reducing surface losses

of phosphorus from crop fields

Conservation tillage

Cropping system that maintains at least 30% of

the soil surface covered with residues after

planting

Conservation cover

Perennial vegetative cover established and

maintained on highly erodible lands where

other BMPs are insufficient to reduce adverse

water quality impacts

Grass filter strip

Permanent sod strip planted at the base of sloping fields or in between the field and surface water bodies

Contour farming

Crops planted on the natural contour of the land to reduce P loss

國立中興大學土壤環境科學系

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Phosphorus BMPs

Sample the tillage layer of soil in each field on a regular basis and have soil analyzed to determine available soil P levels prior to applying P fertilizer.

Credit all available P from manures and other organic residues to the P requirement for the crop.

(Waskom, 1994)

Fertilize soils with ‘low’ to ‘medium’ P soil test values using environmentally friendly and economically sound agronomic guidelines.

In general, soils testing ‘high’ will not respond to additional P and should not receive fertilizer unless a banded starter is needed to compensate for low soil temperatures.

Phosphorus fertilizer should not be applied to soils testing ‘very high’ for soil P.

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When erosion potential is severe, install

structures such as diversions, terraces,

grass waterways, filter fences, and

sediment basins.

Maintain a buffer strip (where fertilizer

and manure is not applied) a safe distance

from surface water and drainage

channels.

Divide large, non- uniform fields into smaller

fertility management units based upon yield

potential or soil type and fertilize according to P

levels determined through soil analysis.

Apply P fertilizers where they can be most

efficiently taken up by the crop. Band application

of P in the root zone reduces surface loss potential

and enhances nutrient availability, especially in

cold or P deficient soils.

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Incorporate surface applied P into the soil

where any potential for surface runoff or erosion exists.

Minimize soil erosion and corresponding P losses by establishing permanent vegetative cover, conservation tillage and residue management, contour farming, strip cropping, and other management practices as feasible.

Maintain grass filter strips on the downhill perimeter of erosive crop fields to catch and filter P in surface runoff.

Manage irrigation water to minimize runoff and erosion.

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Conclusion

Efficient plant nutrition management should

enhance sustainable agricultural production

and safeguard the environment.

Beautiful earth for coming generation